This type of atmospheric furnace is used for brazing of aluminum material to be heated. In this case how to keep good atmosphere in the furnace is important. Conventionally furnace atmosphere brought in to the heating chamber of the furnace through the water cooling chamber etc. is maintained with the sealing chambers like the preheating chamber or the gradual cooling chamber.
These sealing chambers have to be placed before and after the furnace. One of the sealing chambers is located at the entrance of the material to be heated and the other sealing chamber is located at the exit. The sealing chambers have to permit the material to be heated go through and at the same time have to maintain the furnace atmosphere. Consequently the sealing chambers have to have long length. Actually more than one metallic curtains etc. to cover every opening of the sealing chambers were the only solution.